Receive side equalization is a technique by which a signal received on a communications channel is modified to cancel out the distortion caused by the channel. There are many devices that can be used to equalize a signal, for example, finite impulse response (FIR) filters, decision feedback equalizers (DFE), peaking amplifiers, etc.
Equalizers have a number of parameters that are adapted to the channel to cancel as much distortion as possible. Two different sets of techniques exist to compute those parameters: (i) blind equalization; and (ii) adaptive equalization.
With blind equalization, the channel is carefully measured, and the optimal parameters are computed off-line, and then programmed into the equalizer. This technique allows the use of sophisticated mathematical tools to compute the parameters, but fails when the channel has time varying characteristics, or when production numbers are so large that individual measurement of each channel becomes impractical.
With adaptive equalization, the receiver circuitry measures characteristics of the channel together with detecting the data, and computes and applies the parameters of the equalizer, often in a closed loop. This technique allows to compensate for time varying channels, or channels with a large number of manufacturing variations. On the other hand, only primitive channel measurements and simple computations can be performed with the available hardware resources.